<style>
    .bar:hover {
        fill: brown;
    }
</style>
<body>
<script>
    const dataset = [12, 31, 22, 17, 25, 18, 29, 14, 9];

    const w = 500;
    const h = 100;

    const svg = d3.select("body")
        .append("svg")
        .attr("width", w)
        .attr("height", h);

    svg.selectAll("rect")
        .data(dataset)
        .enter()
        .append("rect")
        .attr("x", (d, i) => i * 30)
        .attr("y", (d, i) => h - 3 * d)
        .attr("width", 25)
        .attr("height", (d, i) => 3 * d)
        .attr("fill", "navy")
        // 在下面添加你的代码
        .attr("class","bar")


    // 在上面添加你的代码

    svg.selectAll("text")
        .data(dataset)
        .enter()
        .append("text")
        .text((d) => d)
        .attr("x", (d, i) => i * 30)
        .attr("y", (d, i) => h - (3 * d) - 3);

</script>
</body>